Recyclable, Easily Tearable Packaging Laminate Having A Good Barrier Effect And Method For Production Thereof

ABSTRACT

A recyclable, easily tearable packaging laminate having a good barrier effect, including a first laminate layer and a second laminate layer. The the first laminate layer is a co-extruded, in the machine direction stretched composite consisting of a substrate layer having a high HDPE content of at least 60% by volume, a bonding layer and a barrier layer consisting of a barrier polymer, preferably polyamide or ethylene vinyl alcohol copolymer, having a maximum thickness of 20% of the overall thickness of the first laminate layer. The bonding layer is arranged between the substrate layer and the barrier layer and the first laminate layer is connected on the barrier layer thereof to the second laminate layer.

TECHNICAL FIELD

The present teaching relates to a packaging laminate having a firstlaminate layer and a second laminate layer, the first laminate layercomprising a barrier layer, and a process for producing such a packaginglaminate.

BACKGROUND

In the packaging industry, packaging laminates are used, which shouldhave different proper-ties depending on the application. Such packaginglaminates are usually multi-layer plastic films which are produced byextrusion, co-extrusion (in both cases both flat film and blown film) orlaminating (joining individual layers with a laminating adhesive), ormixtures thereof. Packaging laminates can also include layers that arenot made of plastic, such as a layer of aluminum or paper. The packaginglaminate usually also has an outer sealing layer in order to process thepackaging laminate into the desired packaging, such as a pouch, sack,bag, etc., by thermo-sealing. In another application, a packaginglaminate can also be designed as a shrink film which, depending on theapplication, can also be manufactured in a sealable, but unprintedversion, e.g. for packaging larger portions of meat.

A typical requirement of a packaging laminate is a barrier functionagainst water vapor, oxy-gen and aroma. For this purpose, the packaginglaminate usually contains a barrier layer of aluminum or a suitablebarrier polymer, such as ethylene vinyl alcohol copolymer (EVOH) orpolyamide (PA). Other layers may also be present to give the packaginglaminate the desired properties, such as toughness, stiffness,shrinkability, tear strength, etc. A sealing layer is typically made ofa polyolefin, usually polypropylene (PP) or polyethylene (PE) in thedifferent densities LLDPE, LDPE, MDPE or HDPE.

In order to be able to process the packaging laminate easily, thepackaging laminate must of course not warp or curl, which is whysymmetrical layer structures are usually used.

It is also known that the properties of the packaging laminate can bealtered by mono- or biaxial orientation. Such orientation can beachieved by the extrusion process, for example in a multiple bubbleextrusion process, or only after the extrusion process by stretching thepackaging laminate in the machine direction (in the longitudinaldirection of the packaging laminate) and/or in the transverse direction(normally in the longitudinal direction). The orientation of thepackaging laminate improves in particular stiffness, tensile strengthand toughness. Furthermore, the shrinkage property of the packaginglaminate can be achieved by orientation, and that even rather turbidmaterials, such as HDPE, achieve greater transparency after stretching.

WO 2013/032932 A1 describes such a packaging laminate, for example withthe structure HDPE/bonding layer/EVOH/bonding layer/seal layer, asshrink film. The packaging laminate as a whole is biaxially stretched toproduce the shrink property. This means that stretching can only becarried out after the individual layers of the packaging laminate haveachieved sufficient bond strength. Similar is shown in WO 2009/017588A1. However, WO 2013/032932 A1 and WO 2009/017588 A1 primarily aim at asuitable material for the bonding layer.

EP 673 759 B1 also describes a packaging laminate for a shrink film,with a barrier layer made of EVOH and at least one further polymer layerthat is to be compatible with the barrier layer in terms of stretchingproperties. An anhydride-modified linear low-density polyethylene(LLDPE) is mentioned as an example for the further polymer layer.

WO 2015/175871 A1 in turn describes a packaging laminate consisting ofan HDPE layer bonded to a barrier layer made of, for example, PA,vinyl-containing or acrylate-containing polymers. A sealing layer, e.g.made of LLDPE, may also be arranged at the barrier layer. The aim is toproduce a recyclable laminate in which the barrier layer accounts for amaxi-mum of 5% of the total weight of the packaging laminate. Thepackaging laminate of WO 2015/175871 A1 is not oriented.

In a lot of packaging made of a packaging laminate, it is also desirableto be able to tear the packaging easily by hand, especially for easyopening of the packaging. For example, it is known from WO 2005/113370A1 that it is easier to tear a unidirectionally stretched film parallelto the stretching direction than across it, and that such a filmparallel to the stretching direction can also be torn with reducedtearing force compared to a non-oriented or bidirectionally orientedfilm. Such a film may also be part of a laminate, which may also includea barrier layer of aluminum or EVOH. The unidirectionally oriented filmgives the laminate good tearing properties parallel to the stretchingdirection and essentially prevents tearing across this direction.

EP 1 769 908 A1 describes that a laminate consisting of a barrier layer(e.g. EVOH) and a plastic layer on both sides can easily be torn in bothdirections, if the plastic layer consists of a mixture of PE with adensity between 0.910 g/cm³ and 0.960 g/cm³ (i.e. LDPE, MDPE or HDPE)and a polycyclic olefin, such as a cycloolefin copolymer (COC), and thelaminate is subjected to slight bidirectional stretching. Such lowbi-directional stretching occurs, for example, in blown film extrusion,which means that a separate orientation step of the laminate afterextrusion can be omitted. Due to its COC content, however, such alaminate is only partially recyclable and more complex to produce than apure material. With a high COC content, up to 60% COC in the mixture ismentioned, the laminate is no longer recyclable at all, at least if thePE content also contains larger amounts of LDPE.

SUMMARY

It is an object of the present teaching to specify a recyclablepackaging laminate, which can be easily produced and which is easilytearable in both directions. It is also a task to specify amanufacturing process for such a packaging laminate.

This object is achieved by co-extrusion of a first laminate layerconsisting of a substrate layer with an HDPE content of at least 60% byvolume, a bonding layer and a barrier layer of a barrier polymer,preferably of polyamide or ethylene-vinyl alcohol copolymer, with amaxi-mum thickness of 20% of the total thickness of the first laminatelayer, wherein the bonding layer being arranged between the substratelayer and the barrier layer, by the subsequent stretching of theco-extruded first laminate layer in the machine direction, and by thesubsequent connecting of the thus stretched first laminate layer with asecond laminate layer having a polyethylene content of at least 80% byvolume, wherein the second laminate layer being bonded with the barrierlayer of the first laminate layer. The packaging laminate according tothe present teaching comprises a first laminate layer and a secondlaminate layer, wherein the first laminate layer is a co-extruded, inthe machine direction stretched composite consisting of a substratelayer having an HDPE content of at least 60% by volume, a bonding layerand a barrier layer of a barrier polymer, preferably polyamide orethylene-vinyl alcohol copolymer, having a thickness of at most 20% ofthe total thickness of the first laminate layer, wherein the bondinglayer is arranged between the substrate layer and the barrier layer andthe first laminate layer is bonded to the second laminate layer at thebarrier layer thereof.

The unidirectional stretching of the first laminate layer beforelamination with the second laminate layer significantly increases thebarrier effect of the first laminate layer. In addition, it wassurprisingly found that by unidirectional stretching, the first laminatelayer with the defined structure can be torn equally easily in bothdirections. These tearing properties are impressed on the packaginglaminate, so that the packaging laminate itself can also be torn easilyin both directions. In addition, production is considerably simplifiedby the simple, asymmetrical structure and the merely unidirectionalstretching of the first laminate layer compared to conventionalsymmetrical, bidirectional stretched structures, which alsosignificantly reduces production costs.

A layer stretched in the machine direction (MDO) with a high HDPEcontent, especially if the HDPE content is greater than 80% and above,tends to splice in the longitudinal direction. Therefore, in PEpackaging laminates, such MDO layers with a high HDPE content haveal-ways been combined so far with the tougher LLDPE or mLLDPE, e.g. by afurther layer of LLDPE, whereby a high LLDPE content in the packaginglaminate was aimed for. Surprisingly, it was also found that the firstlaminate layer with such a high HDPE content (even towards 100% HDPE) issufficiently tough even without such a tough LLDPE layer and does nottend to splice. The reason for this is the bonding layer, which givesthe laminate layer the required toughness. The first laminate layer cantherefore also be used advantageously as a barrier film.

Due to the good transparency of the stretched HDPE substrate layer, theoptical properties of the packaging laminate can be improved, if thefirst laminate layer is printed, metallized or coated on the barrierlayer prior to bonding with the second laminate layer. The barriereffect can be further increased by metallizing or coating.

It is advantageous for certain applications, if the first laminate layeron the substrate layer is bonded to another single-layer or multi-layerlaminate layer. The first laminate layer can be printed, metallized orcoated on the barrier layer and/or on the substrate layer. Likewise, atleast one layer of the further laminate layer can be printed, metallizedor coated.

For certain applications it is advantageous, if the first laminate layeron its substrate layer is bonded to a unidirectionally stretched fourthlaminate layer, which has a substrate layer with an HDPE content of atleast 60% by volume, a barrier layer made of a barrier polymer and abonding layer arranged in between. Such a packaging laminate hasparticularly good barrier properties.

[owls] A further advantageous embodiment is obtained, if the secondlaminate layer is a co-extruded, in the machine direction stretchedlaminate consisting of a substrate layer with an HDPE content of atleast 60% by volume, preferably at least 70% by volume and particularlypreferably at least 80% by volume, a bonding layer, a barrier layer of abarrier polymer, preferably of polyamide or ethylene-vinyl alcoholcopolymer, having a thickness of at most 20% of the total thickness ofthe second laminate layer and a sealing layer, wherein the bonding layerof the second laminate layer is arranged between the substrate layer andthe barrier layer of the second laminate layer and the sealing layer isarranged on the substrate layer and wherein the barrier layer of thesecond laminate layer is bonded to the barrier layer of the firstlaminate layer. Such a packaging laminate also has particularly goodbarrier properties. In addition, the sealing layer is advantageouslyintegrated into the co-extruded second laminate layer, so that nofurther manufacturing steps are required for the packaging laminate.

BRIEF DESCRIPTION OF THE DRAWINGS

The present teaching is explained in more detail below with reference toFIGS. 1 to 5, which show exemplary, schematic and non-restrictiveadvantageous embodiments of the present teaching.

FIG. 1 shows a first embodiment of a packaging laminate according to thepresent teaching,

FIG. 2 shows a second advantageous embodiment of a packaging laminateaccording to the present teaching,

FIG. 3 shows a third advantageous embodiment of a packaging laminateaccording to the present teaching,

FIG. 4 shows a fourth advantageous embodiment of a packaging laminateaccording to the present teaching, and

FIG. 5 shows an embodiment of a first laminate layer as a symmetricbarrier film.

DETAILED DESCRIPTION

FIG. 1 shows a packaging laminate 1 according to the present teachingwith a first laminate layer 2 and a second laminate layer 3 connectedthereto.

The first laminate layer 2 in the packaging laminate 1 is stretched inthe machine direction (MDO) and has an asymmetrical layer structure witha substrate layer 4 and a barrier layer 6, which are interconnected by aconnecting layer 5. The thickness of the first laminate layer 2 ispreferably 10 to 40 μm.

Substrate layer 4 has a content of high-density polyethylene (HDPE) ofat least 60% by volume, preferably at least 70% by volume andparticularly preferably at least 80% by volume. The HDPE content canreach up to 100% by volume, but due to common additives (such as slipadditives, anti-block additives, fillers, etc.) 100% by volume isusually never reached. An HDPE is a PE with a density between 0.94-0.97g/cm³. The remainder is a compatible polyolefin material, preferably alow-density linear polyethylene (LLDPE) (with a density between0.87-0.94 g/cm³), a low-density polyethylene (LDPE) (with a densitybetween 0.915-0.935 g/cm³) or also a linear low-density metallocenepolyethylene (mLLDPE), in particular to increase toughness. Any type ofpolyethylene can be considered as a compatible polyolefin material,especially also ethylene copolymers such as ethylene-vinyl acetatecopolymer (EVA), methacrylic acid ethyl ester (EMA), ethylene/acrylicacid copolymer (EAA) or ethylene/butyl acrylate copolymer (EBA).Similarly, polypropylene (PP) or a cycloolefin copolymer (COC) of up to20% by volume can also be used as a compatible polyolefin material. Inthe case of PP, a polypropylene random copolymer with ethylene ascomonomer (usually 5 to 15%), a polypropylene copolymer with ethylene ora polypropylene homopolymer sufficiently compatible with linear PE typessuch as mLLDPE, LLDPE or HDPE is preferably used to achieve at leastlimited recyclability.

The HDPE and the compatible polyolefin material can be present as amixture in substrate layer 4. Substrate layer 4 can also be multilayer(extruded or co-extruded) with one (or more) HDPE layer and one (ormore) layer of the polyolefin material. The thickness of the substratelayer 4 is preferably 5 to 35 μm.

Barrier layer 6 consists of a barrier polymer, i.e. a polymer withsufficient barrier properties, especially against oxygen, hydrogenand/or aroma. The barrier polymer is preferably a polyamide (PA) or anethylene-vinyl alcohol copolymer (EVOH). EVOH is preferred as a barrierpolymer. The barrier layer 6 has a thickness of no more than 20%,preferably 5 to 10%, of the total thickness of the first laminate layer2, i.e. a maximum of 2 to 8 μm. Because of the low thickness of barrierlayer 6 recyclability is not impaired.

The bonding layer 5 serves to connect the barrier layer 6 and thesubstrate layer 4. A sufficient bond adhesion is to be achieved, inparticular to reliably prevent undesired delamination of the firstlaminate layer 2. Suitable bonding layers 5 preferably consist ofpolymers with increased polarity, for example on the basis ofpolyolefins modified with maleic anhydride (such as PE or PP),ethylene-vinyl acetate copolymer (EVA), ethylene/acrylic acid copolymer(EAA), ethylene-butyl acrylate copolymer (EBA) or similar polyolefincopolymers. The thickness of a bonding layer 5 is a maximum of 10% ofthe total thickness of the first laminate layer 2, typically 1 to 5 μm.

The second laminate layer 3 consists mainly of a PE, whereby the PEcontent of the total polymer quantity of the second laminate layer 3without any added mineral substances or other fillers should be at least80% by volume. Various PE types can be used, i.e. LDPE, LLDPE, MDPE,HDPE in pure form or also as a mixture or in the form of co-polymers ormultilayer. The thickness of the second laminate layer 3 is typicallybetween 20 and 200 μm, depending on the application of the packaginglaminate 1.

In the second laminate layer 3, too, the remainder will naturallyconsist of a compatible polyolefin material, as described above, inorder to achieve the desired recyclability.

By using predominantly PE and compatible materials in packaging laminate1, a particularly recycling-friendly laminate can be produced that canbe easily and cost-effectively recycled using conventional methods inmechanical recycling.

The first laminate layer 2 is produced by co-extrusion, because thisallows for particularly simple, cost-effective production. Preferably,the well-known blown film or flat film extrusion process is used.

After co-extrusion, the first laminate layer 2 is stretched exclusivelyin the machine direction (usually the longitudinal or extrusiondirection). The degree of orientation is preferably at least 4:1 in themachine direction. Stretching can take place in-line (i.e. immediatelyafter co-extrusion) or off-line (i.e. at a later point in time afterco-extrusion). Unidirectional stretching can be carried out much moreeasily and cost-effectively than bidirectional stretching, which reducesproduction costs.

It should be noted here that in blown film extrusion and flat filmextrusion, the extrusion gap (1.5 to 2.5 mm for blown film) or the gapof the extrusion nozzle is significantly larger than the final thicknessof the extruded film (typically between 10 and 200 μm). To achieve this,the extruded melt is stretched at temperatures well above the meltingpoint of the extruded polymer, giving it its final thickness. In blownfilm extrusion, for example, the melt is typically stretched in thetransverse direction by about factor of 2 to 3 (the so-called blow-upratio) and in the longitudinal direction by a factor of 1:10 to 1:100(the so-called draw-off ratio). However, this stretching duringextrusion cannot be compared to orientating a plastic film, sinceorientating is usually carried out at temperatures just below themelting point of the polymer in order to permanently align thedisordered polymers and the partially crystalline areas by stretching inthe stretching direction.

An asymmetrical structure of the first laminate layer 2 with anorientation in the machine direction is untypical and has so far beenavoided in practice, especially with blown film, since it was assumedthat such a structure would curl, in particular by absorbing water withthe polar barrier layer 6, which would make further processing moredifficult or impossible. It has been shown, however, that curling in theconcrete design of the structure takes place to an acceptable degreethat does not hinder further processing. It is advantageous to this endwhen the first laminate layer 2 is bonded to the second laminate layer 3very soon after production in order to reduce in particular the waterabsorption of the barrier layer 6. Under certain circumstances it mayalso be necessary or useful to protect the co-extruded film roll withthe first laminate layer 2 from water absorption by means of suitablepackaging until lamination.

The main advantage of the untypical asymmetrical structure of the firstlaminate layer 2, however, is that only a single expensive and lessrigid bonding layer 5 is required. This allows the costs for the firstlaminate layer 2 to be reduced and a stiffer first laminate layer 2 tobe achieved. The higher stiffness is particularly advantageous whenpackaging laminate 1 is used to produce a bag.

Further advantages of the inventive first laminate layer 2 result fromthe stretching. This results in high transparency, especially of thesubstrate layer 4. By stretching the barrier layer, about three to fourtimes higher barrier values are achieved compared to the non-orientedbarrier polymer of the same type, so that less expensive barrier polymercan be used with the same barrier effect. This can significantly reducethe cost of the first laminate layer 2.

It has also come as a surprise that, despite its orientation only in themachine direction, such a first laminate layer 2 can easily be torn byhand in both directions (i.e. in the machine direction and transverse toit), without the film being elongated excessively when torn in thetransverse direction.

The first laminate layer 2 is preferably produced using the blown filmextrusion process, because this results in fewer trim edge waste due toproduction, which leads to lower costs for packaging laminate 1,especially with the more expensive barrier polymers. In blown filmextrusion, more viscous HDPE materials with an MFI (Mass Flow Index) ofless than 3 can also be used. Such HDPE materials have a highermolecular weight and better mechanical properties, which is favorablefor use in a packaging laminate 1. However, such a material would tearparticularly easily in the longitudinal direction and even lead toundesired splicing in the longitudinal direction. This undesirableproperty can be eliminated by incorporating the HDPE material with anMFI of less than 3 in a first laminate layer 2, as described, and evenuniform tearing in both directions can be achieved.

A first laminate layer 2 oriented in the machine direction, with asubstrate layer 4, a barrier layer 6 and a bonding layer 5, as describedabove, does not tend to splice in the longitudinal direction, evendespite the high HDPE content of 60 vol %, and especially also not atvery high HDPE contents of more than 80% by volume to 100% by volume, aswas surprisingly determined. This effect occurs both with anasymmetrical structure of the first laminate layer 2 and with asymmetrical structure of the first laminate layer 2. This observedeffect is proven for a first laminate layer 2 as barrier film by meansof the following examples in Table 1.

TABLE 1 Film A Film B Barrier film C Barrier film D Film 20 20.8 20.620.8 thickness Tensile MD 66 59 51.7 46.9 strength TD 3 11 10 9Elongation MD 52 23 67 30 at break TD 4 12 125 215 Tear MD 2.4 6.5 5.45.6 strength TD 4.1 4.3 6.1 5.4

Table 1 shows the tensile strength in longitudinal direction (MD) andtransverse direction (TD) in N/15 mm and measured according to ASTMD882, the elongation at break in longitudinal direction (MD) andtransverse direction (TD) in % and measured according to ASTM D882 andthe tear strength in longitudinal direction (MD) and transversedirection (TD) in N and measured according to DIN EN ISO 6383-1. Thethickness is the total thickness of the respective film and is given inμm.

Film A in Table 1 is an MDO HDPE mono-film with 10% by volume mLLDPE.Film A is constructed as a five-layer coextrusion film with 10% byvolume mLLDPE in all five, equally thick layers (structure 1/1/1/1/1).The orientation ratio in the machine direction is 6:1. Such a film 1tends to splice in the longitudinal direction, which is particularlyevident from the very low tensile strength and elongation at break inthe transverse direction. The tear strength in the longitudinaldirection is also significantly lower than with the other comparativefilms in Table 1, which is also an indication of the splicing tendencyin the longitudinal direction.

Film B is also a five-layer co-extrudate with a film structure of 95%HDPE+5% LLDPE/100% HDPE/60% HDPE+40% LLDPE/100% HDPE/100% HDPE. Theorientation ratio in the machine direction is 6:1. Thus, in film B, atough component (LLDPE) in higher proportions (40%) was added in atleast one layer to reduce the tendency to splice, as was usual up tonow. This can be seen from the higher values of tensile strength intransverse direction, elongation at break in transverse direction (TD)and tear strength in longitudinal direction compared to film A.

However, the better effect is achieved with a barrier film C. Thebarrier film C is a five-layer co-extrudate with the film structure 95%HDPE+5% LLDPE/100% HDPE/60% HDPE+40% LLDPE/bonding layer 5/EVOH barrierlayer 6. The orientation ratio of the co-extruded barrier film 3 in themachine direction is 5:1. The substrate layer 4 in this film has threelayers (layer thickness 4 μm/4 μm/8 μm) with a HDPE content of ˜78% byvolume in the substrate layer 4. The bonding layer 5 is 2 μm in thebarrier film C, i.e. 10% of the total thickness, and the barrier layer 5is also 2 μm, i.e. 10% of the total thickness. This results in a2/2/4/1/1 structure of the barrier film C. The bonding layer 5 gives thebarrier film C sufficient toughness to significantly reduce the splicingtendency in the longitudinal direction. This can be seen from thesignificantly higher values of elongation at break in the transversedirection (TD) and tear strength in the longitudinal direction. Thetensile strength in the transverse direction is comparable to film B.

It was particularly surprising that for this effect it makes almost nodifference, if the HDPE content in the substrate layer 4 is furtherincreased, as shown by the barrier film D. The HDPE content in thesubstrate layer 4 is also increased. Barrier film D is a five-layerco-extrudate with the film structure of 95% HDPE+5% LLDPE/100% HDPE/100%HDPE/bonding layer 5/EVOH Barrier layer 6. The low LLDPE content in theoutermost layer is primarily used to modify the surface properties ofbarrier film D to improve processing properties. The orientation ratioin the machine direction is again 5:1. The substrate layer 4 in it hasthree layers (layer thicknesses 4 μm/4 μm/8 μm) with an HDPE content of˜97% by volume in the substrate layer 4. The bonding layer 5 in thebarrier film D is 2 μm, i.e. 10% of the total thickness, and the barrierlayer 6 is also 2 μm, i.e. 10% of the total thickness. This results in a2/2/4/1/1 structure of barrier film D. In barrier film D, the tearstrength behavior in the longitudinal and transverse directions is evenparticularly uniform.

In Table 1 only asymmetrical film structures of MDO barrier film 11 aredescribed. For the first laminate layer 2 used as an inventive barrierfilm 11, however, symmetrical structures are also possible (as shown inFIG. 5), for example in the form substrate layer 4 of 100% by volumeHDPE/bonding layer 5/EVOH barrier layer 6/bonding layer 5/substratelayer 4 of 100% by volume HDPE. In one (or both) of the substrate layers4 a low mLLDPE or LLDPE content (e.g. 5 to 10% by volume) could also beadded, preferably in one of the outermost layers to modify theprocessing properties. In such a symmetrical structure, the two outersubstrate layers 4 can also be thicker than the inner layers, e.g. inthe form of an x/1/1/1/x, structure with x>1, in particular x=1.5, 2, 3or 4.

Such a first laminate layer 2 alone as barrier film 11 is also regardedas inventive and is characterized in particular by at least onesubstrate layer 4, which has an HDPE content of at least 60% by volume,preferably at least 80% by volume, and which is bonded via a bondinglayer 5, as described above, to a barrier layer 6, as described above.The substrate layer 4 can also have a multi-layer structure. Inaddition, the barrier layer 6 can be bonded to another substrate layer4, as described above, for a symmetrical structure by means of a furtherbonding layer 5, as described above. Such a barrier film 11 is producedby co-extrusion and subsequent stretching in the machine direction. Thedegree of orientation is preferably at least 4:1 in the machinedirection. Stretching can take place in-line (i.e. immediately afterco-extrusion) or off-line (i.e. at a later point in time afterco-extrusion).

For the production of packaging laminate 1, the stretched first laminatelayer 2 and the second laminate layer 3 are joined together, preferablyby extrusion lamination, extrusion coating or adhesive lamination,wherein the second laminate layer 3 being joined to the barrier layer 6of the first laminate layer 2. In extrusion coating, the second laminatelayer 3 is extruded onto the barrier layer 6 of the first laminate layer2, preferably with an adhesion agent in between. When laminating, thesecond laminate layer 3 is bonded to the barrier layer 6 using asuitable laminating adhesive, for example based on a polyurethaneadhesives or polyolefin copolymers for extrusion lamination. Thethickness of the laminating adhesive is preferably 2 to 5 g/m² forconventional adhesives based on polyurethane or 5 to 20 g/m² forextrusion lamination.

In the case of suitable second laminate layers 3, it has turned out thatthe entire packaging laminate 1 also adopts the tearing properties ofthe first laminate layer 2, i.e. packaging laminate 1 can be tornequally easily by hand in both directions. The first laminate layer 2thus impresses the tearing properties on the packaging laminate 1.

The second laminate layer 3 preferably forms a sealing layer 7, which ina package made of packaging laminate 1 usually faces the packagedproduct. The packaging is produced by cutting, folding andthermo-sealing the packaging laminate 1. Possible packaging productsinclude bags, pouches, sacks, etc.

The second laminate layer 3 can also be multi-layer, for exampleextruded or co-extruded, as indicated in FIG. 2 and described in detailbelow. However, the second laminate layer 3 can also be equipped with abarrier function and can also be stretched, as indicated in FIG. 4 anddescribed in detail below.

In a further embodiment of the packaging laminate 1, as shown in FIG. 2,the first laminate layer 2 is connected on the side of the barrier layer6 to the second laminate layer 3 and on the side of the substrate layer4 to a further laminate layer 10, here a third laminate layer 8. Thethird laminate layer 8 is preferably a single-layer or multi-layerpolymer film, for example a film of predominantly PE (at least 80% byvolume PE), as described with respect to the second laminate layer 3.The third laminate layer 8 can be either extrusion-coated oradhesive-laminated onto the first laminate layer 2, as explained withreference to the sealing layer 7 in FIG. 1. Such a packaging laminate 1according to FIG. 2 can, for example, be used for the production oftubes. In this case, the thickness of the second laminate layer 3 andthe third laminate layer 8 is typically in the range of 150 μm.

It is further indicated in FIG. 2 that the second laminate layer 3 canalso have a multilayer structure, here for example with two layers 7 a,7 b, which form the sealing layer 7. The same applies to the thirdlaminate layer 8. Such a structure of the second laminate layer 3 can,of course, also be provided in an embodiment according to FIG. 1.

It is also possible to metallize and/or print and/or coat (e.g. withalumina or silica) the stretched first laminate layer 2 after stretchingat barrier layer 6 before joining the first laminate layer 2 to thesecond laminate layer 3. Metallization with aluminum is preferred. TheHDPE substrate layer 4 is sufficiently transparent, especially afterstretching, so that the printed image, the metallization or the coatingis visible through the substrate layer 4. Barrier layer 6 can also bepre-treated for printing purposes on the surface to be printed, forexample by corona or flame treatment, to improve the adhesion of theprinting layer to barrier layer 6. Alternatively or additionally, thesubstrate layer 4 can also be printed, metallized or printed, both onthe side facing the barrier layer 6 and on the other side, if necessaryagain after a surface treatment. Common printing processes can be used,such as gravure printing or flexographic printing.

The third laminate layer 8 could also be printed, metallized or coatedon one or both sides, in addition to or as an alternative to the firstlaminate layer 2.

In an advantageous arrangement of the exemplary embodiment of FIG. 2,the barrier layer 6 of the first laminate layer 2 is metallized,preferably with aluminum, in order to increase the barrier effect. Inaddition, the third laminate layer 8 could be printed on the outside.

FIG. 3 describes another exemplary embodiment of an inventive packaginglaminate 1, which can preferably be used for the production of tubes. Inthis embodiment, the first laminate layer 2 is joined to the secondlaminate layer 3 on the barrier layer 6, as in the example in FIG. 1.The first laminate layer 2 is bonded at its substrate layer 4 withanother laminate layer 10, here a fourth laminate layer 2′, which hasthe same structure as the first laminate layer 2 and which is alsounidirectionally stretched. The fourth laminate layer 2′ thus againcomprises a substrate layer 4′, which is bonded to a barrier layer 6′with a bonding layer 5′. The barrier layer 6′ of the fourth laminatelayer 2′ is bonded to the substrate layer 4 of the first laminate layer2, preferably with a suitable laminating adhesive, as described above.These layers of the fourth laminate layer 2′ are constructed andassembled as described above. The fourth laminate layer 2′ consistsprimarily of PE materials with at least 80% PE by volume. However, thethicknesses and the exact compositions or materials of the individuallayers of the first laminate layer 2 and the fourth laminate layer 2′ donot have to match.

Also in this embodiment, the fourth laminate layer 2′ on the substratelayer 4′ and/or on the barrier layer 6′, can be printed, metallized orcoated, additionally or alternatively to the first laminate layer 2. Ina particularly advantageous embodiment, the fourth laminate layer 2′ isprinted, preferably on its barrier layer 6′, and the first laminatelayer 2 is metallized, preferably on its barrier layer 6 or substratelayer 4. This increases the barrier effect of the packaging laminate 1.However, a coating of aluminum oxide or silicon oxide can also beprovided on barrier layer 6 or substrate layer 4 of the first laminatelayer 2 to further increase the barrier effect.

FIG. 4 describes another advantageous embodiment of the presentteaching. In this embodiment the second laminate layer 3 is againmultilayered and comprises a substrate layer 4″, a barrier layer 6″ anda bonding layer 5″, similar to the first laminate layer 2. For theselayers and also for the production of the second laminate layer 3 inthis embodiment, the same applies analogously as above for FIGS. 1 to 3for the first laminate layer 2 or fourth laminate layer 2′. In addition,the second laminate layer 3 in this embodiment comprises a sealing layer7. The sealing layer 7 preferably consists of a PE material, such asmLLDPE, LLDPE, or another suitable thermoplastic, such as polypropylene(PP). However, this second laminate layer 3 with sealing layer 7 stillconsists of at least 80% PE by volume. The sealing layer 7 of the secondlaminate layer 3 is co-extruded with the other layers of the secondlaminate layer 3. The second laminate layer 3 of FIG. 4 is stretchedlike the first laminate layer 2 and as described above. The sealinglayer 7 in this embodiment is thus integrated in a multi-layer,stretched barrier film, which is constructed similarly to the firstlaminate layer 2. This second laminate layer 3 thus has essentially thesame tearing properties as the first laminate layer 2.

In this embodiment, the unidirectionally stretched first laminate layer2 and the unidirectionally stretched second laminate layer 3 are joinedtogether at the abutting barrier layers 6, 6″, preferably by adhesivelamination by means of an adhesive layer 9. A suitable laminatingadhesive is, for example, an adhesive based on polyurethane or apolyolefin copolymer. The thickness of the laminating layer 9 ispreferably 2 to 5 g/m².

Also in this embodiment, one (or more) of the layers of the packaginglaminate 1 can be printed, metallized or coated.

Of course, in the embodiment the first laminate layer 2 could also havean additional laminate layer 10 (e.g. a third laminate layer 8 or fourthlaminate layer 2′ as described above), as indicated in FIG. 4.

The packaging laminate 1 in accordance with the present teaching thushas at least one asymmetrical, unidirectionally stretched, firstlaminate layer 2 of at least 60% HDPE by volume with a substrate layer4, a barrier layer 6 and a bonding layer 5 and a second laminate layer 3bonded thereto, which forms a sealing layer 7, with a PE content of atleast 80% by volume. As described above, a further single-layer ormulti-layer laminate layer 10 (e.g. a third laminate layer 8 or fourthlaminate layer 2′) with a PE content of at least 80% by volume can bearranged on this packaging laminate 1, on the side of the first laminatelayer 2 facing away from the second laminate layer 3. This furthersingle-layer or multi-layer laminate layer 10 is thus bonded to thesubstrate layer 4 of the first laminate layer 2.

In packaging made of a packaging laminate 1 in accordance with thepresent teaching, the sealing layer 7 of the packaging laminate 1advantageously faces the inside of the packaging.

By printing on at least one layer of the first laminate layer 2, thesecond laminate layer 3 or the further laminate layer 10 of a packaginglaminate 1 according to the present teaching with a barrier lacquer, forexample polyvinyl alcohol (PVOH), the barrier effect of the packaginglaminate 1 can be further increased also in this way. Such lacquerlayers can be applied very thinly, typically in the range of 0.5 to 2.0g/m², and thus do not impair the recyclability of packaging laminate 1.

Finally, it should be noted that each of the individual layers describedabove can also have a multi-layer structure in the first laminate layer2, the second laminate layer 3 or the further laminate layer 10 itself.

1. A method for producing a packaging laminate comprising: Coextruding afirst laminate layer with a substrate layer having an HDPE content of atleast 60% by volume, a bonding layer and a barrier layer, the barrierlayer having a barrier polymer and having a thickness of at most 20% ofthe total thickness of the first laminate layer, wherein the bondinglayer is in between the substrate layer and the barrier layer;Stretching the first laminate layer in machine direction only; andBonding a second laminate layer having a polyethylene content of atleast 80% by volume to the barrier layer.
 2. The method according toclaim 1, comprising printing and/or metallizing and/or coating the firstlaminate layer before bonding to the second laminate layer.
 3. Themethod according to claim 1, comprising bonding the substrate layer to afurther single-layer or multi-layer laminate layer having a polyethylenecontent of at least 80% by weight.
 4. The method according to claim 3,comprising printing and/or metallizing and/or coating the barrier layerand/or on the substrate layer before bonding to the further laminatelayer.
 5. The method according to claim 3, further comprising printingand/or metallizing and/or coating at least one layer of the furtherlaminate layer.
 6. The method according to claim 1, further comprising:providing an another multi-layer laminate layer with a substrate layerwith a HDPE content of at least 60% by volume, a barrier layer having abarrier polymer, and a bonding layer in between, wherein the anotherlaminate layer is unidirectionally stretched, bonding the barrier layerof the another multi-layer laminate layer to the substrate layer of thefirst laminate layer.
 7. The method according to claim 1 comprising:coextruding the second laminate layer with a substrate layer having aHDPE content of at least 60% by volume, a bonding layer, a barrier layerhaving a barrier polymer and having a thickness of at most 20% of thetotal thickness of the second laminate layer and a sealing layer,wherein the bonding layer is in between the substrate layer and thebarrier layer of the second laminate layer, and the sealing layer isarranged on the substrate layer, stretching the second laminate layer inmachine direction; and bonding the barrier layer of the second laminatelayer to the barrier layer of the first laminate layer.
 8. A packaginglaminate comprising a first laminate layer and a second laminate layer,the first laminate layer is stretched in machine direction only andcoextruded with a substrate layer with a HDPE content of at least 60% byvolume, a bonding layer and a barrier layer, the barrier layer having abarrier polymer and having a thickness of at most 20% of the totalthickness of the first laminate layer the bonding layer is arrangedbetween the substrate layer and the barrier layer, the first laminatelayer is bonded to the second laminate layer via its barrier layer. 9.The packaging laminate according to claim 8, wherein the barrier layerof the first laminate layer is printed, and/or metallized and/or coated.10. The packaging laminate according to claim 8 wherein the firstlaminate layer is bonded on its substrate layer to a furthersingle-layer or multi-layer laminate layer having a polyethylene contentof at least 80% by volume.
 11. The packaging laminate according to claim10 wherein at least one layer of the further laminate layer is printedand/or metallized and/or coated.
 12. The packaging laminate according toclaim 10, wherein the further laminate layer is stretched in machinedirection and co-extruded and comprises a substrate layer with a HDPEcontent of at least 60% by volume, a barrier layer having a barrierpolymer and a bonding layer arranged in between, wherein the substratelayer of the first laminate layer is bonded to the barrier layer of thefurther laminate layer.
 13. The packaging laminate according to claim 8,wherein second laminate layer is stretched in machine direction and isco-extruded with a substrate layer having a HDPE content of at least 60%by volume, a bonding layer, a barrier layer having a barrier polymer andhaving a maximum thickness of 20% of the total thickness of the secondlaminate layer, and a sealing layer, wherein the bonding layer of thesecond laminate layer is in between the substrate layer and the barrierlayer of the second laminate layer, and the sealing layer is arranged onthe substrate layer, wherein the barrier layer of the second laminatelayer is bonded to the barrier layer of the first laminate layer. 14.The method according to claim 1, wherein the barrier layer comprisespolyamide and/or ethylene-vinyl alcohol copolymer.
 15. The packinglaminate according to claim 8, wherein the barrier layer comprisespolyamide and/or ethylene-vinyl alcohol copolymer.
 16. The packinglaminate according to claim 8, wherein the substrate layer of the firstlaminate layer has a HDPE content of at least 70% by volume.
 17. Thepacking laminate according to claim 13, wherein the substrate layer ofthe second laminate layer has a HDPE content of at least 70% by volume.18. The packing laminate according to claim 12, wherein the barrierpolymer of the further laminate layer comprises a polyamide and/or anethylene-vinyl alcohol copolymer.
 19. The packing laminate according toclaim 13, wherein the barrier polymer of the second laminate layercomprises a polyamide and/or an ethylene-vinyl alcohol copolymer.
 20. Apackaging laminate, comprising: a composite being co-extruded with asubstrate layer, a barrier layer and a bonding layer; the bonding layerarranged in between the substrate layer and the barrier layer; thesubstrate layer having a HDPE content of at least 60% by volume; thebarrier layer comprising a barrier polymer and having a thickness of atmost 20% of the total thickness of the composite; the composite beingstretched in one direction only; and a laminate layer bonded to thebarrier layer or the substrate layer of the composite.